This invention relates to a cutting tool, sometimes more commonly referred to as a cutting insert, for simultaneously facing and grooving a target surface, for example, of a thermoplastic or thermosetting material including non-celled, open-celled and closed-celled elastomers such as urethane particularly suited to be used for creating a planarized polishing surface of a chemical mechanical planarization (CMP) pad with uniform groove dimensions.
A CMP pad is a required element in a CMP process for the planarization of various materials and devices used in the semiconductor and other industries. The CMP pad is a consumable part that is applied on the tool of a CMP equipment. In general a CMP pad has pores and/or groove patterns that act as carriers of chemicals used for planarization and a planarized polishing surface that mechanically assists in the planarization process.
Conventionally, the base material for a CMP pad is individually formed by a cast molding, thermoforming, injection molding or other molding or extrusion process, or individually skived or sliced from a large block of the raw material. Generally a CMP pad is finished by mechanically removing the excess material, creating coplanar surface portions, and a single surface on one side is featured with some groove patterns. The mechanical method for finishing the CMP pad may be by means of a semi-automated or a fully automated CNC lathe, a horizontal milling machine, a vertical milling machine, a cylindrical grinding machine, or arbors with orbital cutting tools in series.
Dimensionally, a CMP pad is required to be of even thickness and without warp. The polishing surface of a CMP pad must satisfy at least the following three requirements. Firstly, it must be provided with a carrier mechanism for the slurry on the CMP pad surface, which can be pores, holes, grooves or other types of topography. Secondly, it must be parallel to the backside of the pad. Thirdly, it must be of a textured roughness without any irregularities such as bumps, burrs, or any other protruding features not only on the surface but also within the carrier mechanism. Carrier mechanisms, such as pores and holes, are usually a characteristic feature of the base material or may be die-punched into the base material. Groove patterns, serving as a carrier mechanism, may be of various dimensions and designs and may be either molded or mechanically cut into the planarized surface.
Individually molded CMP pads may have groove patterns and topography directly molded into the raw material by an injection molding or another molding or casting process. Productivity of CMP pads is greatly enhanced by this process, but there are other problems associated with the direct molding of CMP pads. For the control of even thickness, creating coplanar surface portions, and creating a warp-free CMP pad, the process control for direct molding of CMP pads is very difficult. The roughness and textured surface of a CMP pad are not controllable by direct molding due to the heat and transition of the resin from a liquid state to a solid state. There are also limitations regarding accuracy in the geometry and depth of the groove and topography due to the difficulty in removing the CMP pad from its mold or cast. The same problem limits the flexibility of the CMP pad design and makes it difficult to create different groove geometries and deeper grooves for a longer lasting CMP pad. In a production setting, as a CMP pad is worn and becomes thinner, the desired topography and groove geometry are likely to become lost. As the CMP pad becomes too thin, its grooves may become too shallow to serve as an effective carrier mechanism for the slurry.
The conventional method of mechanically creating a polishing surface of an evenly thick, warp-free CMP pad with coplanar surface portions and a specified groove pattern has been to do it in two separate steps (or processes), that is, the grooving process and the facing process. The order in which these two processes are to be carried out may or may not be important, depending on the methods and accuracy of the mechanical equipment. In conventional machining methods, the separation into these two processes was necessary since they required separate cutting tools or cutting inserts. By having two separate processes, there were inherently the problems of increased cost and inefficiencies in the manufacturing. A two-step manufacturing process requires two sets of tools, maintaining two inventories, changing the tools from one process to the other, prolonging the cycle time due to the tool changes, and reduced productivity due to separate tool calibrations, maintenance, and repairs. The facing and grooving processes are sometimes accomplished with two separate machines. This requires additional capital investment, utilities, facility space, tools, parts, and equipment operators.
Other consequences of conventional machining or mechanical methods of cutting grooves by using conventional cutting inserts include the bumps, burrs, and other protruding or overhanging irregularities that are likely to form on the pad surface or within the groove itself. These irregularities often become the source of loose particulates that may become left on the pad surface or trapped within the groove. The level of these irregularities and particulates may vary from one pad to another, and this causes inconsistency in the performance of CMP pads.